Effect of gonadal hormones on enzyme activities in brain and pituitary of male and female rats.

Gonadectomized male and female rats were treated with equimolar doses of estradiol benzoate (EB) or testosterone pripionate (TP) daily for one week and enzyme activities were measured in the basomedial hypothalamus, corticomedial amygdala, and pituitary. In females, the hypothalamus showed estrogen-dependent increases in glucose-6-phosphate dehydrogenase (G6PDH), isocitrate dehydrogenase (ICDH), and malate dehydrogenase (MDH). Activities of ICDH and MDH were elevated in the amygdala. In the pituitary, estrogen administration resulted in increased levels of G6PDH, 6-phosphogluconate dehydrogenase (6PGDH), and lactic dehydrogenase (LDH). The estrogen antagonist, MER-25, effectively blocked estrogen-dependent increases in pituitary G6PDH and 6PGDH. Administration of TP did not result in changed enzyme levels. In males, treatment with EB and TP resulted in significant elevations in some but not all enzymes that were increased by EB in the female. Estrogen-dependent increases of activity in males were noted in pituitary G6PDH, 6PGDH, and LDH, in hypothalamic MDH, and in amygdaloid ICDH. Administration of TP led to increased levels of pituitary G6PDH, 6PGDH, LDH, ICDH, and MDH, hypothalamic ICDH and G6PDH, and amygdaloid MDH. The pattern of enzyme changes found in male and female brain and pituitary is discussed in relation to behavioral responses to gonadal hormones, nuclear uptake of gonadal hormones, and metabolism of androgen.